Such modules are well known and, in view of their small thickness and their flexibility, they are principally intended to form part of small-sized products. Amongst these products should, in particular, be noted: electronic cards also called "smart cards", such as credit cards, parking cards, telephone call cards etc., as well as electronic watch movements.
A method of mass producing electronic-timepiece modules, having a thin circuit and electronic components, is for example described in detail in French patent FR 2 412 225. This method consists essentially in providing an insulating tape-like film by way of substrate, sticking onto this film a thin metal strip, forming the patterns of conductors by photolithography and in so doing eliminating the non-usable part of the strip whereby the substrate and conductors define the circuits, connecting the electronic components to these conductors, and finally separating the thus-obtained modules from their support-serving film by stamping.
This manner of proceeding however has several drawbacks. Firstly, the processing of the metal tape by photolithography apart from being long and expensive involves chemically etching the metal with a solvent which by producing ionic pollution of the insulating film reduces the long-term reliability of the modules. Secondly, due to the fact that photolithographic processing forms electrically insulated conductors, if the modules include an electronic component such as an integrated circuit sensitive to electrical discharges the modules will also be very sensitive to such discharges in the final stages of their manufacture, or during storage.
Another method of mass producing circuits for modules having the advantage of not requiring etching is described in Swiss Patent CH 608 314. It consists in providing an insulating film, also in tape form, and sticking on this film a metal strip in which the conductors have been pre-cut by stamping, each conductor remaining connected to the rest of the strip by one of its ends. However, simultaneously with the sticking operation, the conductors are also cut from the strip. Hence this method, like the previous one, produces circuits with insulated conductors and therefore modules that are not protected against electric shocks.
The methods known from the prior art therefore have the drawback of including a step of removing all excess metal from the strip, leaving on the substrate of the circuits only conductors in their final form and which therefore are electrically insulated.